With the extension of the high-speed transmission, more and more cable connectors including a greater number of signal lines than in the prior art have come to be used in the personal computer and the large-capacity memory device. On the other hand, the cable connector is required to be compact. Therefore, a multiplicity of signal lines are arranged with high density in the connector. In such a cable connector, the distance between the signal lines is so short that each signal line is required to be accurately connected conductively to the substrate by soldering, etc.
Japanese Unexamined Patent Publication No. 2003-109708, for example, discloses a multicore high-speed signal transmission connector in which “the thickness of an insulator plate is determined in such a manner that a pair of uncoated terminals are fitted on signal contacts arranged on the upper and lower surfaces of the insulator plate to hold the insulator plate from the upper and lower sides thereof without changing the pitch of the terminal pair at the end of each of a plurality of two-core cables are connected to a pair of the signal contacts arranged on the upper and lower plate surfaces.”
Also, Japanese Unexamined Patent Publication No. 2006-260850 discloses a cable connector having “a configuration comprising a contact assembly so structured that contacts are built in an electrically insulating block unit, a relay substrate with an end connected to the contact on the back of the contact assembly and the other end having terminal pads juxtaposed, a cable having a plurality of coated wires each including a wire and an electrically insulating coating for coating the wire and a shield case covering the contact assembly, the relay substrate and the ends of the cable, wherein the forward ends of the wires of the coated cable are arranged fixedly on the terminal pad of the relay substrate, and wherein the portion of the wire of the coated cable exposed from the end of the coating is thinner than the wire, the thinned wire portion being fixed on the terminal pad.”
Further, Japanese Unexamined Patent Publication No. 2004-31257 discloses “a cable connector connected with a plurality of balanced transmission cables, comprising a connector fitted on the mating connector, a signal contact and a ground contact held on the connector, a locator for holding the cable and a ground plate held on the locator, characterized in that the balanced transmission cable includes a plurality of signal lines and drain wires insulated from each other, the ground plate is connected with the drain wires, and the connector and the locator engage each other, so that the ground plate and the ground contact are interconnected while at the same time collaborating with each other to surround each of the signal lines of the plurality of the balanced transmission cables.” In soldering a plurality of signal lines of a cable to a substrate, the wiring pattern formed on the substrate and each signal line are required to be set in position accurately. This positioning operation is generally difficult, and some conventional connectors include a somewhat complicated structure for the positioning requirement.
Also, in the case where the cable connector is used for high-speed transmission, the impedance is disturbed at some points in the connector. Specifically, in the internal portion of the cable where the signal lines are covered with an insulating coating with the outer periphery thereof covered by a conductive ground layer such as a copper foil, the distance between each signal line and the ground layer is constant along the length of the cable, and therefore, the impedance is also constant. On the other hand, a wiring pattern of a specified size is formed on the substrate of the cable connector, and therefore, the impedance of the portions subsequent to the substrate is also specified at a predetermined value. In the portion of each signal line with the coating thereof cut off and the end thereof soldered to the wiring pattern on the substrate, therefore, the exposed signal line is arranged adjacently to another signal line, sometimes resulting in the impedance disturbance. This impedance disturbance tends to increase especially in the high-speed transmission of high frequency, and once the disturbance exceeds a predetermined value, the waveform is disturbed and the signal quality reduced.
Accordingly, an object of at least one embodiment of this invention is to provide a structure of a multicore cable connector with a multiplicity cables aligned and electrically connected to the wiring pattern formed on the substrate, wherein the alignment and the soldering of the cable signal lines and the substrate wiring pattern are facilitated using a simple structure and the impedance disturbance on the substrate is suppressed to a minimum.